The present invention relates to a silicone condensation and/or equilibration catalyst, and its use to effect the condensation or equilibration of silanol containing organopolysiloxanes.
One of the procedures which can be used to equilibrate organopolysiloxanes is based on the use of a linear phosphonitrilic chloride (LPNC) having the formula EQU Cl.sub.3 P(NPCl.sub.2).sub.n NPCl.sub.3. PCl.sub.6, ( 1)
where n is 0-4 and preferably 0-2. In addition to compounds shown by formula (1), other LPNC-type materials, such as Cl.sub.2 PONCl.sub.3, or "PONP", have also have been found to be effective as catalysts. These materials, hereinafter collectively designated "phosphorus-nitrogen chloride", can be made by procedures involving the use of PCl.sub.5 and an ammonium salt, as shown by U.S. Pat. No. 3,839,388, incorporated herein by reference. Such phosphorus-nitrogen chlorides can be used as catalysts to intercondense silanol-terminated polydiorganosiloxanes, as well as to equilibrate triorganosiloxy-terminated polydiorganosiloxanes. Mixtures of silanols and diorganosiloxanes having terminal triorganosiloxane units also can be equilibrated with these catalysts. For example, U.S. Pat. No. 2,990,419 shows a method for making organopolysiloxane oils by equilibrating a hydroxy-endblocked diorganosiloxane and a triorganosilyl-endblocked diorganosiloxane using a phosphorous-nitrogen compound, such as a phosphonitrilic halide. In addition, U.S. Pat. No. 3,835,388 shows the use of vacuum in combination with a phosphonitrilic halide as an equilibration catalyst to facilitate the condensation and/or equilibration of silanol fluids. Although effective results can be achieved using these methods, faster catalysts and new procedures are constantly being sought to improve the efficiency of silicone gum manufacture.